# The Cat In The Hat Comes Back

Contributed anonymously

Materials

The Cat in the Hat Comes Back
A top hat -- plastic ones can be found very cheaply in costume stores (optional)
A cat's tail -- also found in costume stores (optional)

Dr. Seuss's stories are great tools in the computer science classroom. The Cat in the Hat Comes Back is one of the stories in which students can visualize recursion at work.

The basic story (for those of you who have forgotten) is about a cat in a hat that needs to clean up a spot. He decides that the job is too big to do alone so he lifts his hat and out pops Little Cat A (a smaller version of the cat in the hat).Little Cat A looks at the spot and decides that they need yet more help with this job. Little Cat A lifts his hat, and another, even smaller, cat appears. Little Cat A says:

This is Little Cat B.
And I keep him about,
And when I need help,
Then I let him come out.

This procedure of requiring help continues until finally Little Cat Z appears and cleans the spot. When the job is finished, the cats, one by one, return to their hats.

I begin teaching recursion by reading The Cat in the Hat Comes Back to my class (with an enthusiastic interpretation). The kids love it. I don't read the entire story. I bookmark certain pages and read an abbreviated version. And I wear a top hat (with a stuffed animal cat inside of it) and a cat tail!